heating chamber with a fan guard

Abstract: A heating apparatus of the present invention relates to a high speed oven having a turntable mechanism for heating food products by utilizing a combination of jet impingement of heated air (a jet impingement) and microwaves or either of them, the apparatus comprising a safety device and an exhaust device. This invention has the following configurations: a turntable mechanism for enabling the turntable to be preferably rotated, the turntable including openings at the central part thereof so that the heated air and microwaves can pass therethrough; a limiter mechanism for removing overload imposed on the turntable by utilizing only a mechanical operation; an apparatus provided with scarfed areas on upper and lower boards of the heating chamber so that the food products can be baked uniformly even when utilizing a jet impingement technique; a fan guard comprising a switch activation means for activating a switch for allowing a generation of the heated air, which switch is positioned at the outside of the heating chamber, only when the fan guard is fixed to the heating chamber; a heating apparatus which simplifies operations for connecting exhaust tubes upon a number of apparatuses being stacked on each other; and a turntable driving mechanism for preventing contaminants from flowing into a gap between a connecting shaft and an axis receptor.

Description: BACKGROUND OF THE INVENTION The present invention relates to a heating chamber with a fan guard removably fixed to an inside of a heating chamber in front of a means for generating heated air which is to be transmitted into the inside of the heating chamber. Such a heating chamber is known form US-A-5,205,274. DESCRIPTION OF THE PRIOR ART Though attempts have been made in the past to improve the cooking oven, there still remains a lot of problems to be solved. Regarding the cooking oven, in particular one for use both in business and in homes, there has been a strong demand for a cooking apparatus which enables the time needed for cooking to be shortened and maintains and improves delicate cooking qualities of baked products, such as temperature, baking color, flavor, smell, and so on. A microwave oven utilizing inductive heating generated by a microwave can raise the temperature inside the food products in a short time, so that the time needed for cooking can be shortened. However, the cooking qualities, such as finish, baking color, flavor, and smell of the food products are not good. Accordingly, the microwave oven may, in practice, be regularly used for re-heating and thawing of the food products, but only rarely used for the final cooking stage of the baked products. To overcome the above drawback in the microwave oven, there is an oven in which inside heating and surface heating are combined, that is, while the inside of the food is heated with microwaves, its surface is heated by air convection at a high temperature and radiation of infrared rays, the oven further comprising a turntable mechanism on which the food product can be mounted, so that it can be heated more uniformly. However, the balance of the cooking finish of the food product may be lost, because the velocity needed to accomplish the inside heating with microwaves is slower than that needed to accomplish the surface heating. As a result, if a heating velocity is adjusted to the cooking finish for the surface heating, the inside of the food will be heated too much, and thus the food may be too tough and savory water and juice will be removed from the food. As a result, the time needed for cooking will not be shortened very much. On the other hand, if the heating velocity is adjusted to the time needed for raising the temperature of the inside of food product, all of the surface may not be sufficiently heated. Thus, although the cooking time can be made shorter, the quality of the food can not be maintained. To solve these above problems, Mr. Donald Paul Smith, an American, invented an apparatus in which air at a high temperature is ejected from a plurality of small holes separated from each other to impinge the air onto the upper and lower surfaces of the food product, so that the surfaces can be heated at a rate two or four times faster than a conventionally used forced convection heat transfer apparatus, it being possible for the apparatus to utilize microwaves for the inside heating of the food product (U.S. Patent No.3,884,213). The heating principle and method invented by Mr. Smith are very effective, enabling the time needed for cooking to be shortened and cooking quality to be improved. However, such an apparatus having, in practice, the above benefits has not yet appeared in the market. The reason for this is as follows. Although the above apparatus can be used as an apparatus for all baking dishes for all the dry-types of heating, such as baking, boiling, barbecuing, griddling, roasting, and fry cooking not using oil, oils and juices might be dispersed in the oven at the time of cooking depending on the kind of cooking method and the food product to be cooked. As a result, these oils and juices would be baked, carbonized and finally accumulated on wall surfaces and many portions in the oven due to the high temperature. This would cause many troubles, for example, a locking of the removable portions in the oven and a local heating resulting from a generation of microwave sparks. Accordingly, the level of the cleaning performance on the inside of the oven is very important for the above type of oven. However, even if the cleaning performance of the apparatus is improved, providing of such elements as the jet impingement mechanism, a microwave mechanism and a turntable makes the structure of the apparatus complicated, thus making the cleaning performance ineffective. In the prior apparatus, an apparatus has been provided comprising a structure which activates a door switch (a micro switch is typically used) when the door is opened by the users, so that the rotation of the fan motor can be stopped. If such an apparatus is used for an apparatus whose door is very frequently opened and closed, in particular, when it is used for the purpose of obtaining quick service, the fan of such an apparatus may be frequently stopped, thus causing problems in performance, function, and durability. A fan guard is typically provided in front of the fan and the heater, so as to prevent the user from touching them. In this case, it is desirable to make it possible to remove the fan guard from the heating chamber, so that the cleaning performance can be improved, and also the fan guard can be taken out from the heating chamber at the time of cleaning. In an oven also utilizing microwave heating, the fan guard is often adapted to function as a shield board against microwaves. In this situation, since it is not easy to remove such a fan guard, and thus the cleaning performance is not always good, it has been desired to improve the oven by adapting a part other than the fan guard to have it a function as a shield board, so that the fan guard can be removed from the heating chamber for baking using a strong flame. However, when the fan guard is made removable, it sometimes happens that the oven will be used under such a condition that it is forgotten to reset the fan guard in the heating chamber after its cleaning operation is finished. Thus, there is a possibility that the fan will be activated without re-setting the fan guard, and as a result, the user might be injured by the rotating fan and the heater when his fingers are inserted into the heating chamber. Also, there is a possibility that the fan and heater may be activated in error, while an operation for resetting the cleaned fan guard in the heating chamber is being performed. Thus, it has been desired to provide the fan guard which is not only removable from the apparatus, but prevents the user from forgetting to reset the fan guard. SUMMARY OF THE INVENTION The present invention aims to find a solution to the above-mentioned problems. As a solution to this problem, the present invention provides a heating chamber with a fan guard as defined in claim 1. Preferred embodiments of the inventive heating chamber are set out in claims 2 and 3. BRIEF DESCRIPTION OF THE DRAWINGS The above and related objects, features and advantages of the present invention will be more fully understood by reference to the following detailed description of the preferred embodiments of the present invention when taken in conjunction with the accompanying drawings wherein; Fig.1 is a perspective schematic illustration of the fan guard in accordance with one embodiment of the present invention. Fig.2 is a partly sectional fragmentary view of the fan guard in Fig.1 as seen from the direction of the arrow "A" thereof. Fig.3 is a partly sectional fragmentary view of the fan guard in Fig.1 as seen from the direction of the arrow "B" thereof. Fig.4 is an enlarged view of the fan guard in Fig.1 as seen from the direction of the arrow "C" thereof. Fig.5 is a sectional view taken along the line I-I of the heating apparatus in Fig.1 provided with the fan guard in Fig.1. Fig.6 is a sectional view taken along the line III-III of the heating apparatus in Fig.1 provided with the fan guard in Fig.1. Figs.1 to Fig.4 illustrate a heating apparatus having a fan guard of the present invention. Fig.1 is a perspective, schematic illustration of the fan guard according to one embodiment of the present invention. Fig.2 is a partly sectional fragmentary view of the fan guard in Fig.1 as seen from the direction of an arrow "A" in Fig.1 Fig.3 is a partly sectional fragmentary view of the fan guard in Fig.1 as seen from the direction of an arrow "B" in Fig.1. Fig.4 illustrates an enlarged view of the fan guard in Fig.1 as seen from the direction of an arrow "C" in Fig.1. As seen from these Figures, the fan guard comprises a fan guard plate 41, having a spiral shape so as to define a circulation wind air plenum at two places between an upper inside wall and a lower inside wall of the heating chamber 1, when the fan guard plate 41 is attached to the inside of the heating chamber 1. A bell mouth member 53 is formed at the center of the fan guard plate 41 for sucking air. Further, a fan guard net 42, parts of which are appropriately separated from each other, is attached to an opening of the bell mouth 53 of the fan guard plate 41, so as to prevent a user from inserting in error his hand or fingers into the opening. A holder rail 46 is attached to the lower side of the fan guard plate 41. The holder rail 46 is made of a metallic tube and is provided with an axis receptor 48 at the inside of the front end portion thereof. As clearly shown in Fig.1, a guide fixing groove 46A having an almost L-shape is formed at the outside periphery of the metallic tube of the holder rail 46. A magnet holder 45 is secured to the holder rail 46 in such a way that the holder can be moved along the inside of the axis receptor 48 of the holder rail 46. The front end portion of the magnet holder 45 is provided with a magnet 43 made from rare earth elements having a good demagnetizing characteristic at a high temperature. The magnet 43 is accommodated in a magnet case 44 for protecting the magnet 43 from being damaged, and concentrates a magnetic flux on the front end portion of the magnet holder 45. A holder lug 47 is provided near the end of the magnet holder 45 opposite to the end on which the magnet 43 is attached. The magnet lug 47 is projected to the outside of the holder rail 46 through the L-shape guide fixing groove 46A formed in the holder rail, so as to enable the user of the heating apparatus to operate the magnet holder 45 by hand. As shown in Figs.1 to Fig.3, when the holder lug 47 is positioned in a groove portion corresponding to a shorter leg of the L-shaped guide fixing groove 46A, the magnet holder 45 is fixed in position so that it can not be moved in either a right or left direction. To move the magnet holder 45 under such a fixed condition, the holder lug 47 must be operated to rotate the magnet holder 45 in the axis receptor 48, so as to move the magnet lug to a groove position corresponding to a longer leg of the guide fixing groove 46A, and further move it in the left direction in the Figures along the longer leg of the groove 46A, thereby moving the magnet holder 45 in a left direction which results in the movement of the magnet 43 from a fixed position to a pulled back position. To move the magnet 43 from the pulled back position to the fixed position as shown in Fig.1 to Fig.3, an operation the reverse of the above is used. Fig.5 is a sectional view taken along the line I-I of the heating apparatus in Fig.1, comprising the fan guard of the present invention. Fig.6 is a sectional view of the heating apparatus, taken along the line III-III. Referring now, in particular, to Figs.5 and 6, a description will be given of an operation for fixing the fan guard as explained in connection with Fig.1 to Fig.4 of the invention at a predetermined position within the heating chamber of the heating apparatus. The fan guard can be removed from the front side of the heating chamber 1 of the heating apparatus. upon setting and removing the fan guard, the holder lug 47 is operated to slide the magnet holder 45 into the pulled back position thereof, so that the magnet case 44 accommodating the magnet 43 can be moved to be in a plane of the fan guard plate 41. In an inner part of the heating chamber 1, the fan 5 driven to be rotated by the fan motor 7 is positioned. The heater 6 is disposed at the inner periphery of the fan 5. The fan guard 8 is removably positioned at the front portion of the fan 5 within the heating chamber 1. To accomplish this, a fixing pin 62 is provided on the upper portion of the side wall of the heating chamber 1, and a magnet case guide 49 is provided on the lower portion thereof. The magnet case guide 49 is embedded in a thermal insulant 57, so as to prevent the atmosphere in the heating chamber 1 from leaking out. The magnet case guide 49 has a tube shape of which a f ront end portion is closed, the tube shape enabling the magnet case 44 to be fit into the magnet case guide 49, the magnet case 44 being attached to the front end portion of the magnet holder 45 of the fan guard 8. A magnet close switch 50 is fixed, at the outside of the heating chamber 1, to a portion apart by a predetermined distance from a front end portion of the magnet case 44. The magnetic close switch 50 may be connected to an electric circuit for applying electrical power to the fan motor 7 and the heater 6, and be designed to be almost opened, but then closed when the fan guard is fixed to the inside of the heating chamber 1, thereby sliding the magnet holder 45 to insert the magnet case 44 into the magnet case guide 49. The fan guard 8 can be mounted on and fixed to a predetermined position in the heating chamber 1, by setting the fan guard at the predetermined position in front of the fan 5 in the heating chamber 1, engaging the upper portion of the fan guard plate 41 to the pin 62 provided on the inside wall of the heating chamber 1, and then sliding the magnet holder 45 from the pulled back position, so as to fit the magnet case 44 into the magnet case guide 49. Thus, the holder rail 46, axis receptor 48, magnet holder 45, magnet 43 and magnet case 44, mounted on and fixed to the fan guard plate 41, can partially constitute a means for fixing the fan guard to the inside of the heating chamber 1. Thus, in accordance with the fan guard of the present invention, when the fan guard is properly fixed to the predetermined position in the heating chamber 1, since the magnet close switch 50 is closed by utilizing the activation of the magnet 43, the fan and the heater will be correctly operated by switching on the electric power for the electric circuit incorporating the fan motor and the heater. On the other hand, since the magnet close switch 50 is still kept open as long as the fan guard 8 is correctly fixed to the predetermined position in the heating chamber 1, turning on of the power source for the fan 5 and heater 6 will not cause the activation of the fan 5 and the heater 6. The magnet close switch 50 is positioned close to the magnet case guide 49 which has a high temperature due to its nature. In this embodiment, to prevent heat from being transmitted from the magnet case guide 49, fresh air is made to flow out from the part between the magnet case guide 49 and the magnet close switch 50. For the configuration to accomplish the above function, a cooling fan 54 is additionally provided for introducing the fresh air from a plurality of intakes 59 opened at the bottom of the cladding 56, passing the air between the magnet case guide 49 and the magnet close switch 50, and finally exhausting the air to the outside thereof via the fan 54. The fresh air is obtained from a plurality of holes 58A, which holes are provided on a side surface of the leg 58 positioned at the bottom of the cladding 56. Thus,the leg 58 can be positioned at more inner parts of the front side of the apparatus body than the cladding 56, and thus make the operation for obtaining the fresh air possible, even if the cladding 56 comes in contact with another perpendicular wall. As is clearly shown in Fig.5, in a condition that the fan guard is attached and secured to a predetermined position within the heating chamber 1, the air plenums 61 for circulating wind are defined at the upper and lower portions of the heating chamber 1. Thus, when the fan 5 is driven to rotate it, the sucking air from the bell mouth 53 of the fan guard plate 41 is heated by the heater 6 disposed at the central part of the fan 5, and thus the heated air is blown away from the upper and the lower air plenum 61 into the heating chamber 1. Also, as shown in Figs.5 and 6, to insulate the heating chamber 1, the surrounding outside perimeter of the heating chamber 1, except for the front end portion of the magnet case guide 49, is covered with insulating materials 57. The fresh air from the fresh air intakes 59 cools the surface of the insulating materials 57 when it flows over the surfaces of the materials. The magnet case guide 49 makes it easy to insert and take out the magnet case 44 thereinto or therefrom by having a diameter at its opened side larger than that at its closed side at the front end. In the embodiment above mentioned, while the magnet 43 has been described as being used for a switch activator and the magnet close switch 50 as being used for the heat air generator, they are not limited to such applications, as any combination is all right if it accomplishes the above same functions.

Claims: Heating chamber with a fan guard removably fixed to an inside of the heating chamber (1) in front of a means (5,6) for generating heated air which is to be transmitted into the inside of the heating chamber (1), characterized by a switch activation means (43,44,45) for activating a means (50), positioned at an outside of the heating chamber (1) for allowing generation of the heated air when said fan guard (41,42) is fixed to the heating chamber (1), said switch activation means (43,44,45) constituting a part of a means (62,44,48,49) for fixing the fan guard (41,42) to the heating chamber (1), said switch activation means (43,44,45) being adapted to be engaged with an attachment place (49) provided on a corresponding position on a wall surface of the heating chamber (1), said means (50) for allowing generation of the heated air being disposed at a position at the outside of the heating chamber (1) corresponding to said coresponding position of said attachment place (49). The heating chamber according to claim 1, wherein said switch activation means (43,44,45) comprises a magnet (43), and said means for allowing generation of the heated air is a magnet closing switch (50). The heating chamber according to claim 2, further comprising a means (54) for cooling an area around said magnet closing switch (50).

Inventors: MATSUO HIROSHI, TSUKAMOTO HIDEKI, UEOKA AKIO, MATSUO, HIROSHI, TSUKAMOTO, HIDEKI, UEOKA, AKIO, Matsuo, Hiroshi, c/o Fujimak Corporation, Tsukamoto, Hideki, c/o Fujimak Corporation, Ueoka, Akio, c/o Fujimak Corporation
Applicants: FUJIMAK CORP, FUJIMAK CORPORATION
Application year: 1994
Main classification: F24C7
IPC codes: F24C7, F24C15, H05B6, A21B1